I’ve bought a few things from them over the years and the experience has been fine. I don’t like that you don’t complete checkout on Audiogon, you get routed to their website and, in my case, they slapped on sales tax which I hadn’t seen mentioned up front.
The one time I requested a quote from them on a $3000 item they offered me $2300. So I wouldn’t bother selling anything to them unless it was a part-ex deal.
Since you have to pack it and ship it to them anyway, I don’t see why you wouldn’t just sell it yourself directly and pocket some extra cash.